Spy in the sky: ‘Tis the season for satellite-spotting

Satellites have now returned to our skies. These brilliant drifting lights cross the sky every few minutes – even if many folks say that they’ve never seen one. A good teacher can create astonishment by pointing up and saying, “That’s a military spy satellite, but it’s no longer operational.” How could he know that?

It’s easy: Satellite familiarity is effortless. No telescope is needed, not even much patience. However, there is a preferred time of year, a “satellite season.” It’s now.

From April through September, dozens of bright outer-space machines cross the sky every hour. More than 6,000 satellites currently orbit the Earth, and during the first 90 minutes of darkness one appears every minute or two. If it’s a slow-moving point of light and not a plane, it’s either a satellite or a UFO mothership.

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A dozen years ago the Iridium company launched an armada of special communications satellites with huge solar panels. These catch the sunlight and suddenly flash. They go from invisible to dazzling and back again in a few seconds. This is a big source of UFO reports.

The Heavens Above website lets you enter your home’s latitude and longitude, and it will calculate the next week’s Iridium flashes and exactly where in the sky they’ll be. I highly recommend it if you’re interested in these things. For example, Woodstock will see a sudden flash as bright as Venus this Friday evening (the 20th) at 9:46:46, halfway up the sky in the east-northeast. The next night it’ll repeat at 9:40:37 in the same spot, but less brilliantly.

With a little practice you can easily recognize different speeds that correspond to various heights aloft. The higher it orbits, the slower a satellite moves. A typical military or communications satellite travels in a 250-to-600-mile-high orbit and traverses the sky in a couple of minutes.

Satellites never go east-to-west. They’re launched the opposite way, to match the Earth’s rotation. Planners take advantage of our planet’s 1,040-mile-per-hour spin by sending the rocket eastward to give it an initial push. That’s why all countries launch from as close to the Equator as they can, where rotation is fastest. We didn’t pick Cape Kennedy because of its proximity to the place that would become Disney World, nor did the French choose Guiana because they like the wine there.

Some satellites have a polar orbit – instantly recognizable because they’re heading more or less south-to-north or vice versa. It’s a favored military trajectory, because it allows the whole Earth to be scrutinized each day.

Okay, so it’s a spy satellite. What can it see? Claims of satellites being able to read the license plates of cars are exaggerated – but not by very much. Resolution of the US KH-11 in the 1990s was reportedly in the eight-inch range, allowing a passing satellite to see you taking a stroll, but not notice your bald spot. Last month I had a long conversation with a former Air Force spy satellite optics expert. He was able to discuss non-classified details, and assured me that instruments virtually as sharp as the Hubble Telescope are pointed the other way: downward to the ground. Because of the inherent blurriness of the atmosphere, even sophisticated enhancement techniques cannot (he confirmed) identify individuals.

Satellites merely shine by reflected sunlight, and their complex shapes reflect unevenly. If the machine is functional and stable, one side may hold the sun for quite some time. But in the case of defunct satellites, the inevitable out-of-control tumbling causes obvious changes in brightness as they move across the sky.

Of the 24,000 satellites tracked since 1957 – of which a third are still in orbit – many are debris just a few inches in diameter. They are not our problem, as observers. Of the 3,000 actual payloads currently in orbit, only some 300 satellites are large enough and low enough to stand out easily to the naked eye. They are typically the size of a schoolbus.

The visibility of satellites varies, simply because of the changing sunlight that reaches them. Obviously, the Sun is shining in space, even when it’s nighttime here on the ground below. The Moon, for example, always basks in sunlight; otherwise we wouldn’t see it. No matter how dark the night, the Sun’s often shining “up there.” But not always: When we look into the midnight sky, we’re staring right into our own planet’s shadow – into a black sunless zone that extends into space for a million miles. So you want to observe during the first 90 minutes after nightfall.

Spend five minutes looking up, and you’ll see some, guaranteed. And they’ll see you, too – even if they cannot yet know you by name.